GPSS Compiler/Simulator

As with any large software project, the first priority of this thesis is program correctness in the GPSS compiler and correct simulation statistics. Several distinct processes are gone through in the construction of any compiler/simulator: development of specifications, indication of the goals, design, implementation, evaluation, and maintenance. The specifications of the GPSS compiler/simulator were introduced in the thesis proposal. The VAX/VMS 11/750 will be the machine which this GPSS compiler/simulator uses because of the supported \u27C language, a Command Language Definition Utility, and accessibility by this author. The implementation language, \u27C, was chosen based on ease of readability, ease of understanding, the simple but powerful data structures in the language, and the language\u27s support of modularization. Three milestones were identified for this thesis project: the parser, the pseudo code generator, and the simulator. Many projects are started with only the end product in mind, but the goals which were identified constitute essential checkpoints to validate the integrity of the compiler/simulator. There were three distinct design phases due to the milestone identification. The parser design encompassed the initial modular design layout of the source code for the entire compiler, and the design of the symbol table. Design of the pseudo code language had two constraints imposed: the ease of representation of the GPSS language in twoaddress code and the ease of integration of the pseudo language into the parser. Last but by no means unimportant was the design of the simulator, which controls the order of events within a model. After each design phase described above was completed, the implementation or writing of the source code was accomplished. The parser, the pseudo code generator, and the simulator carried through the \u27C capabilities of modularization and readability. Evaluation of the compiler was accomplished at three points: after the implementation of the parser, after the implementation of the pseudo code generator, and after the implementation of the simulator. The milestones or checkpoints specified in the identification of goals were essential in verifying the integrity of the system. Although maintenance is not a part of this thesis, the design phase took into consideration the ease of adding functionality to the implemented subset of GPSS. This compiler/simulator could be used as a base from which a more sophisticated and current version of the GPSS language would immerge